Javascript 对象枚举

Question

在控制台中将 "property" 放入/更改为 this[property] 有什么区别，我相信两者都指的是相同的表达式，但后者给了我 [object , Object] 当我调用函数时。

var rockSpearguns = {
    Sharpshooter: {barbs: 2, weight: 10, heft: "overhand"},
    Pokepistol: {barbs: 4, weight: 8, heft: "shoulder"},
    Javelinjet: {barbs: 4, weight: 12, heft: "waist"},
    Firefork: {barbs: 6, weight: 8, heft: "overhand"},
    "The Impaler": {barbs: 1, weight: 30, heft: "chest"}
};

rockSpearguns["listGuns"] = function(){
    for (var property in this) {
        if(this[property]["heft"]!==undefined){
            console.log("Behold! " + this[property] + ", with " +
            this[property]["heft"] + " heft!");
        }
    }
}

rockSpearguns["listGuns"]();

Answer 1

property 将是被循环对象的键("Sharpshooter", "Pokepistol", ...)字符串。

this[property] 将是所有对象的对象的值。将对象与字符串连接时，通过调用其函数 toString 将对象转换为字符串。所以:

var obj = {};
var string = "Hello. I'm " + obj;

等同于:

var obj = {};
var string = "Hello. I'm " + obj.toString();

obj.toString() 在这种情况下将返回 [object Object]"。

关于括号和点符号，这里是 MDN 上的文档.